• Title/Summary/Keyword: shock formation

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Numerical Simulation of the Effect of Finite Diaphragm Rupture Process on Micro Shock Tube Flows

  • Arun Kumar, R.;Kim, Heuy-Dong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2012.05a
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    • pp.309-317
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    • 2012
  • Recent years have witnessed the use of micro shock tube in various engineering applications like micro combustion, micro propulsion, particle delivery systems etc. The flow characteristics occurring in the micro shock tube shows a considerable deviation from that of well established conventional macro shock tube due to very low Reynolds number and high Knudsen number effects. Also the diaphragm rupture process, which is considered to be instantaneous process in many of the conventional shock tubes, will be crucial for micro shock tubes in determining the near diaphragm flow field and shock formation. In the present study, an axi-symmetric CFD method has been applied to simulate the micro shock tube, with Maxwell's slip velocity and temperature jump boundary conditions. The effects of finite diaphragm rupture process on the flow field and the shock formation was investigated, in detail. The results show that the shock strength attenuates rapidly as it propagates through micro shock tubes.

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Investigation of the shock structural formation of the supersonic nozzle jet with longitudinal variation of coaxial pipe location

  • Roh, Sung-Cheoul;Park, Jun-Young;Kim, Soo-Yong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.784-788
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    • 2004
  • A visualization study of shock formation of the supersonic jet nozzle using a Shadowgraph Method (SM) was carried out to investigate the effect of the longitudinal variation of coaxial pipe end tip position inside the supersonic nozzle. The experiment was performed for the Mach number range from 1.1 to 1.2 at nozzle exit. The well known shock cell structure was shown with the pipe end located deep inside the nozzle for the studied Mach number. With the pipe end approaches nozzle exit, it was found that the shock cell structure disappeared and turned into complex formation. In order to understand the mechanism of the shock structural change, computational simulation was carried out using the Navier-Stokes solver, FLUENT. Topological sketch was added with an aid of the visualization and the numerical simulation.

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Numerical Simulation of the Effect of Finite Diaphragm Rupture Process on Micro Shock Tube Flows (Micro shock tube 유동에 대한 유한 격막 파막과정의 영향에 관한 수치 해석적 연구)

  • Arun Kumar, R.;Kim, Heuy Dong
    • Journal of the Korean Society of Propulsion Engineers
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    • v.17 no.3
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    • pp.37-46
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    • 2013
  • Recent years have witnessed the use of micro shock tube in various engineering applications like micro combustion, micro propulsion, particle delivery systems etc. The flow characteristics occurring in the micro shock tube shows a considerable deviation from that of well established conventional macro shock tube due to very low Reynolds number and high Knudsen number effects. Also the diaphragm rupture process, which is considered to be instantaneous process in many of the conventional shock tubes, will be crucial for micro shock tubes in determining the near diaphragm flow field and shock formation. In the present study, an axi-symmetric CFD method has been applied to simulate the micro shock tube, with Maxwell's slip velocity and temperature jump boundary conditions. The effects of finite diaphragm rupture process on the flow field and the shock formation was investigated, in detail. The results show that the shock strength attenuates rapidly as it propagates through micro shock tubes.

Effect of Prophylactic Supplementation of Vitamin E and Se on Antioxidant Enzymes during Endotoxic Shock in Buffalo Calves

  • Sandhu, T.S.;Singha, S.P.S
    • Asian-Australasian Journal of Animal Sciences
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    • v.16 no.11
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    • pp.1577-1582
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    • 2003
  • This study was conducted to determine the effects of prophylactic supplementation of vitamin E and Se on oxidative damage and antioxidant status. Fifteen healthy male buffalo (Bubalus bubalis) calves between the age of 6 to12 months were divided into three groups of five animals each: Group I-control, group II-endotoxic shock group infused with lyophilized E coli endotoxin @ 5 ${\mu}g$/kg body wt, and group III-supplemented with vitamin E @ 250 mg and Se @ 7.5 mg, one month prior to induction of endotoxic shock. All the animals in group II and group III exhibited signs of endotoxic shock. When the endotoxic shock was induced, there was significant (p<0.05) increase in the circulating levels of malonyl dialdehyde MDA (an indicator of lipid peroxidation). In the supplemented group III the magnitude of formation of MDA was also less as compared to group II at every stage of study. There was significant (p<0.05) decrease in circulating levels of SOD, GSH-Px, Catalase and G-6-PD activity from the normal (0 h) value with passage of time. As a result of endotoxic shock, these values reached a lowest value, and then showed a tendency towards the 0 h value. Prophylactic supplementation with vitamin E and Se was successful in reducing the quantum of oxidative damage due to formation of free radicals because of endotoxic shock.

CLUSTERS OF GALAXIES: SHOCK WAVES AND COSMIC RAYS

  • RYU DONGSU;KANG HYESUNG
    • Journal of The Korean Astronomical Society
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    • v.36 no.3
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    • pp.105-110
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    • 2003
  • Recent observations of galaxy clusters in radio and X-ray indicate that cosmic rays and magnetic fields may be energetically important in the intracluster medium. According to the estimates based on theses observational studies, the combined pressure of these two components of the intracluster medium may range between $10\%{\~}100\%$ of gas pressure, although their total energy is probably time dependent. Hence, these non-thermal components may have influenced the formation and evolution of cosmic structures, and may provide unique and vital diagnostic information through various radiations emitted via their interactions with surrounding matter and cosmic background photons. We suggest that shock waves associated with cosmic structures, along with individual sources such as active galactic nuclei and radio galaxies, supply the cosmic rays and magnetic fields to the intracluster medium and to surrounding large scale structures. In order to study 1) the properties of cosmic shock waves emerging during the large scale structure formation of the universe, and 2) the dynamical influence of cosmic rays, which were ejected by AGN-like sources into the intracluster medium, on structure formation, we have performed two sets of N-body /hydrodynamic simulations of cosmic structure formation. In this contribution, we report the preliminary results of these simulations.

COSMIC RAYS ACCELERATED AT SHOCK WAVES IN LARGE SCALE STRUCTURE

  • RYU DONGSU;KANG HYESUNG
    • Journal of The Korean Astronomical Society
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    • v.37 no.5
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    • pp.477-482
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    • 2004
  • Shock waves form in the intergalactic space as an ubiquitous consequence of cosmic structure formation. Using N-body/hydrodynamic simulation data of a ACDM universe, we examined the properties of cosmological shock waves including their morphological distribution. Adopting a diffusive shock acceleration model, we then calculated the amount of cosmic ray energy as well as that of gas thermal energy dissipated at the shocks. Finally, the dynamical consequence of those cosmic rays on cluster properties is discussed.

RuO2-Doped TiO2 Nanotube Membranes Prepared via a Single-Step/Potential Shock Sequence

  • Yoo, Hyeonseok;Seong, Mijeong;Choi, Jinsub
    • Journal of Electrochemical Science and Technology
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    • v.10 no.3
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    • pp.271-275
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    • 2019
  • Anodic $TiO_2$ nanotubes were simultaneously grown and doped with $RuO_2$ by single-step anodization in a negatively-charged $RuO_4{^-}$ precursor. Subsequently, a high positive voltage was imposed on the nanotubes in an $F^-$-based electrolyte (a process referred to as potential shock), which led to the formation of a through-hole $RuO_2$-doped $TiO_2$ nanotube membrane without significant loss of the $RuO_2$ catalyst. XPS results confirmed that the doped Ru metal was converted into $RuO_2$ as the potential shock voltage increased. Further increases in the potential shock voltage led to the formation of $RuO_x/Ru$ in the $TiO_2$ nanotubes. All of our results clearly showed that a through-hole catalyst-doped $TiO_2$ nanotube membrane can be produced by a sequence consisting of single-step anodization and the potential shock process.

Studies on the Protoplast Formation of Cellulomonas flavigena and its Observations under Scanning Electron Microscope (Cellulomonas flarigena의 원형질체 형성과 주사전자현미경적 연구)

  • Bae, Moo;Lee, Eun-Ju
    • Microbiology and Biotechnology Letters
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    • v.14 no.2
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    • pp.175-179
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    • 1986
  • In order to develope a protoplast fusion of the genus Cellulomonas having high assimilibility of cellulose, the optimum conditions for the protoplast formation of Cellulomonas flavigena NCIB 12901 was investigated and observed by means of Scanning Electron Microscope. The results suggested that the susceptibility of the cell wall by lysozyme treatment on protoplast formation was considerably depend on the cultural periods of the cells. Cells of C. flavigena at mid exponential phase could more efficiently convert to protoplast cells than those at late exponential phase did. The rate of the protoplast formation was 95%, even though the rate was over 99.9% on counting by indirect method after osmotic shock treatment, when cells of the organism at mid exponential phase were treated with lysozyme (400$\mu\textrm{g}$/$m{\ell}$) for 6 hours and observed by SEM. In the evaluation of protoplast formation of the genus Cellulomonas, direct method of the observation under Scanning Electron Microscope was much more reliable than the counting method of protplasts after osmotic shock treatment. Because defferences between the number of spheroplast and protoplast were not able to be figured out on counting the number of protoplast after osmotic shock treatment.

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TRAFFIC FLOW MODELS WITH NONLOCAL LOOKING AHEAD-BEHIND DYNAMICS

  • Lee, Yongki
    • Journal of the Korean Mathematical Society
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    • v.57 no.4
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    • pp.987-1004
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    • 2020
  • Motivated by the traffic flow model with Arrhenius looka-head relaxation dynamics introduced in [25], this paper proposes a traffic flow model with look ahead relaxation-behind intensification by inserting look behind intensification dynamics to the flux. Finite time shock formation conditions in the proposed model with various types of interaction potentials are identified. Several numerical experiments are performed in order to demonstrate the performance of the modified model. It is observed that, comparing to other well-known macroscopic traffic flow models, the model equipped with look ahead relaxation-behind intensification has both enhanced dispersive and smoothing effects.

VARIABILITY OF BOW SHOCK LOCATION AT MARS

  • Yi, Yu;Kim, Eo-Jin;Kim, Yong-Ha;Kim, Jhoon
    • Journal of Astronomy and Space Sciences
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    • v.16 no.2
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    • pp.139-148
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    • 1999
  • Bow shock formation, in case the supersonic solar wind flow is hindered by the atmosphere of Mars, is investigated. The atoms newly ionized from the extensive neutral atmosphere of Mars are loaded to the solar wind. By the conservation of momentum, the solar wind velocity is decreased. Then the supersonic flow velocity drops to the subsonic flow velocity in front of Mars at certain region, which is called the bow shock. The location of Mars subsolar bow shock is highly varying in the range of 1.3 to 2.5 Rm. Martian bow shock location is estimated by one-dimensional flux tube equations reduced from full three-dimensional MHD equations. The variability of Mars bow shock location effected by the solar wind conditions is studied. It is evident that the solar wind dynamic pressure change is able to make the Mars bow shock location variable.

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